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Mill <br /> Creek — ----- -- - <br /> A, sstwiates Water Resource and Environmental Consulting <br /> November 8, 1994 I <br /> Mike Infurna NOV 1 4 1994 <br /> San Joaquin County Environmental Health Division <br /> P.O. Box 388 ENVIRONMENTAL HEALTH <br /> Stockton, CA 95201-0388 PERMIT/SERVICES <br /> RE: Site Investigation Workplan <br /> Souza/Nicolaw Properties, Byron Road, Tracy, CA <br /> Dear Mr. Infurna, <br /> I am writing to present a workplan for performing a site <br /> investigation of hydrocarbon contamination at the above referenced <br /> properties. Previous work has been performed for Citation Homes on <br /> parcel #238-08-02 by Terrasearch Inc. , in 1990 and 1994 . The <br /> results of these phases of investigation have previously been <br /> submitted to your office. This workplan covers both the parcel <br /> previously investigated by Terrasearch and the adjacent parcel to <br /> the west (Figure 1) . At this time the property owners want to <br /> characterize the site adequately prior to proceeding with site <br /> development. <br /> Because the extent of contamination in soil and groundwater at the <br /> site is not completely defined we propose to install 6 monitoring <br /> wells to a depth of approximately 10 feet below first encountered <br /> groundwater (estimated 5 +/- feet) at the locations shown on the <br /> attached site plan (Figure 2) . Wells will be completed from <br /> surface to 5 feet with 2 inch PVC casing and from 5 to 10 feet with <br /> . 010 inch factory slotted PVC screen. Due to the proximity of the <br /> ground surface the sand pack will extend only 0. 5 feet above the <br /> top of the screen slots. These well borings will be sampled at a <br /> minimum of five foot intervals for logging purposes. A soil sample <br /> will also be collected from just above the saturated zone and <br /> submitted for laboratory analysis. These samples will be analyzed <br /> for Benzene, Toluene, Ethylbenzene and Xylenes (BTEX) and Total <br /> Gasoline Hydrocarbons as gas, diesel and crude oil (TPHG/D/C) by <br /> standard EPA/DOHS methods. <br /> Upon completion the new wells will be developed by surging and <br /> pumping until turbidity is minimized. The wells will be purged 48 <br /> hours later. A minimum of three well volumes (casing and <br /> sandpack) will be removed using pH, temperature and electrical <br /> conductivity stabilization as parameters for estimating sample <br /> representativeness. A water sample from each well will be <br /> submitted for BTEX and TPHG/D/C analysis. Prior to sampling, water <br /> levels will be obtained from all site wells. All wellheads will be <br /> surveyed to a common datum. Laboratory services will be provided <br /> by Appollo Analytics Inc. , a State Certified Laboratory. <br /> Post Office Box 130 0 Milford, Ca. 96121 • Ph. 916-253-2155 9 Fax 916-253-2294 <br />